The present invention relates to a one-way clutch, and more particularly to a compact one-way clutch which has a reduced width.
As a one-way clutch which transmits relative rotation between a shaft and a housing in one direction, and which runs idle in the other direction, known is a roller clutch which is shown in a section view taken parallel to the axis of FIG. 23, and a section view taken perpendicular to the axis of FIG. 24. Such a roller clutch is often used in a reel of a fishing gear, a sheet feeding mechanism of a copying machine, and the like.
The roller clutch is configured by: an outer race 10; a shaft 11 which functions also as an inner race; a plurality of rollers 12 which are interposed between the outer race 10 and the shaft 11; a cage 13 which retains the rollers 12 at constant intervals in the circumferential direction; and springs 14 which urge the rollers 12 in respective constant directions. Flanges 10a are formed on the outer race 10. A plurality of cam surfaces 10b are formed at constant pitches on the inner face of the outer race 10. Each of the cam surfaces 10b is configured by a face in which a distance with respect to the surface of the shaft 11 is gradually reduced in a constant direction (the direction of the arrow a in FIG. 20) along the circumferential direction. Each of the rollers 12 is urged in the direction along which, under the state where the roller is retained by the cage 13 fixed to the inner side of the outer race 10, the roller between the cam surface 10b and the shaft 11 is caused by the corresponding spring 14 to bite the cam surface 10b, i.e., the direction along which the distance with respect to the shaft 11 is reduced. As a roller clutch of this kind, also a clutch of a structure in which another inner race is interposed between the roller and the shaft is known.
In the above configuration, when the shaft 11 is rotated with respect to the outer race 10 in the direction of the arrow A in FIG. 24, for example, the rollers 12 which receive the rotation force are displaced against the urging force of the springs 14, in the direction along which the distance between the cam surfaces 10b and the shaft 11 is increased, and the rollers 12 run idle with respect to the outer race 10. As a result, the rotation force of the shaft 11 is not transmitted to the outer race 10, and the shaft 11 runs idle with respect to the outer race 10. By contrast, when the shaft 11 is rotated with respect to the outer race 10 in the direction of the arrow B in FIG. 24, the rollers 12 are displaced by the rotation force and the urging force of the springs 14, in the direction along which the distance between the cam surfaces 10b and the shaft 11 is reduced, and enter between the cam surfaces 10b and the shaft 11. As a result, the rotation force of the shaft 11 is transmitted to the outer race 10, and the outer race 10 is rotated together with the shaft 11.
In the above, the example in which coil springs the number of which is equal to that of balls are used as the springs 14 for pushing the rollers 12 has been described. In consideration of the easiness of the assembling step, and the like, practically, springs having structures such as shown in FIGS. 25 and 26 are often used as the springs 14.
In the structure shown in FIG. 25, a resin-made cage 13 and an annular plate spring 14 are combined with each other. In this structure, claws 14a which enter pockets 13a of the resin-made cage 13 to push respective rollers in a constant direction along the circumferential direction are formed integrally on the plate spring 14, and caulking claws 14b are formed integrally on both the axial ends. When the caulking claws 14b are caulked, the plate spring 14 in a state where it is integrated with the resin-made cage 13 is mounted inside the outer race 10.
In the structure shown in FIG. 26, a cage and a spring are integrally formed by a resin. Claws 13b which push the rollers 12 are integrally projectingly formed in pockets 13a of the cage 13, respectively.
In such a roller clutch, because of process restrictions or the like, the rollers 12 must have a length of a certain degree or more, and hence the reduction of the overall width (the dimension in the axial direction) is inevitably limited. This is similarly applicable also to a one-way clutch in which, in place of rollers, sprags are used as power transmission members.
In the above-mentioned roller clutches, as shown in FIGS. 25 and 26, the springs for urging the rollers 12 have a complicated structure. This is a cause of an increased cost.
The above-mentioned roller clutches is not provided with means for performing positioning with respect to the shaft 11 in the axial direction. Therefore, there is a further problem in that a mechanism for positioning must be additionally disposed.
The invention has been conducted in view of such circumstances. It is an object of the invention to provide a practical one-way clutch in which the width can be reduced as compared with one-way clutches including a conventional roller clutch, means for urging power transmission members can be further simplified, it is not required to additionally dispose a mechanism for positioning in the axial direction, and, because of this also, the overall width can be largely reduced as compared with a conventional roller clutch.